1. Field of the Invention
The present invention relates to a recording medium having a data structure for managing reproduction of text subtitle data and methods and apparatuses of recording and reproducing.
2. Description of the Related Art
Optical disks capable of storing large amounts of high-quality digital video/audio data, for example, DVDs (digital versatile disks), and DVD recording/reproducing apparatuses are now commercially available.
Text subtitle data, such as caption data to be superimposed on main video data is recorded on a DVD as image data (e.g., BMP data). An optical disk reproducing apparatus reproduces the subtitle image data along with the main video data from the DVD and displays the main data and text subtitle data on an external display apparatus connected to the optical disk reproducing apparatus.
A user of such an optical disk reproducing apparatus, therefore, can view the main video data of a DVD overlaid with related subtitle text data using a display apparatus.
Recently, the standardization of new high-density optical disks having higher recording density than a DVD has been progressing rapidly. The Blu-ray Disc ROM (BD-ROM) is one example of these new optical disks. In addition, methods for managing text subtitle data, which are capable of displaying the main video data of a BD-ROM with superimposed captions by recording image data of subtitles on the BD-ROM (e.g., BMP data), and control information, for display control of the image data on the BD-ROM, have been proposed.
In the case where the text subtitle data is recorded as image data such as BMP data, the character attributes of the recorded text subtitle data (e.g., the character font and the character size) cannot be changed or a large amount of image data for displaying the subtitle in various ways is additionally required. A method of effectively managing text subtitle data for a high-density recording medium such as an optical disk is not yet available.